Intake of tomato-enriched diet protects from 6-hydroxydopamine-induced degeneration of rat nigral dopaminergic neurons

Abstract

There is extensive evidence that oxidative damage of dopamine (DA)-containing neurons in the substantia nigra pars compacta (SNc) may contribute to the pathogenesis of Parkinson’s disease (PD). We evaluated the potential neuroprotective effect of diets enriched with wild-type Red Setter (RS) tomato or transgenic High Carotene (HC) tomato, rich in β-carotene, obtained by the activation of lycopene β-cyclase (tlcy-b), in an animal model of PD. Male Fischer 344 rats were fed for 14 days with standard AltrominMT diet, 5% RS- or 5% HC-enriched diet. Seven days after the beginning of this diet regimen, the rats were lesioned by 6-hydroxydopamine (6-OHDA) injected into the left SNc. After further 7 days, the rats were sacrificed, and DA and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in both the left (ipsilateral) and the right (contralateral) striata were measured. Striatal DA levels were reduced by 86.5 ± 5.0% in control, 86.2 ± 5.0% in HC-, and 56.0 ± 9.0% in RS-fed group. Striatal DOPAC was decreased by 85.6 ± 5.0% in controls, 83.0 ± 6.0% in HC-, and 58.9 ± 10.0% in RS-fed group. Blood was obtained from the rats on day 14 and the plasma level of licopene and β-carotene was measured by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) for the determination of lycopene and β-carotene levels. The plasma level of lycopene was 4.7 ± 0.2 ng/ml in 5% RS-fed rats, while it was undetectable (< 2.5 ng ml−1) in control and HC-fed rats. The efficacy of RS diet to preserve striatal dopaminergic innervation can be attributed to the ability of lycopene to prevent the degeneration of DA-containing neurons in the SNc.